Combining HRTEM-EELS nano-analysis with capacitance-voltage measurements to evaluate high-kappa thin films deposited on Si and Ge as candidate for future gate dielectrics
Résumé
Aberration corrected transmission electron microscopy and electron spectroscopy are combined with electrical measurements for the quantitative description of the structural, chemical and dielectric parameters of rare earth/transition metal oxides thin films. Atomic structure near the interface and elemental profiles across the interface up to the surface of La-doped ZrO2 and Er-doped HfO2 films prepared by atomic layer deposition on Si(100) and Ge(100) are determined. Interfacial layers unavoidably form between the semiconductor substrate and the dielectric oxide after deposition and annealing. They are evidenced from a structural and chemical point of view. From the knowledge of the chemical extent of the interfacial layer and of the accumulation capacitance of the stack, it is possible to recover the dielectric constant of both the interfacial layer and the high-κ oxide layer constituting the stack using a multi-layers capacitor model approach. Oxides with permittivities higher than 30 are stabilized. Interfacial layers, silicate/germanate in composition, with permittivites, respectively, tripled/doubled compared to the one of SiO2 are evidenced.